A wide range of solutions are known for separating out the various components, with different chemical reactions or even physical effects being exploited for the particular component which is to be separated out and may be in elemental form or in the form of a chemical compound.
In many cases, gas mixtures of this type are purified by means of solid substances, in which case the separation is effected by sorption. In this case, in each case the usable surface area of the substance used plays a role in ensuring a higher separation capacity. It is known that it is possible to increase surface area by means of the geometric configuration and in particular the specific surface area of a substance by means of the porosity.
However, it is known that porosity and mechanical strength are precisely contradictory, and consequently limits are imposed on the porosity. Limits are also imposed on the use of strength-increasing binders, since the latter have an adverse effect on the separation properties.
Hitherto, correspondingly suitable substances, mainly chemical compounds in granule form with a very wide range of grain sizes, have been used to separate out components, and a suitable porosity has often been set by corresponding sintering.
The gas mixture which is to be purified or from which a component is to be removed is then passed through a fixed bed formed from a bulk mass of the granules and the component to be separated out is in each case removed by sorption. The bed in this case forms a throttling area for the gas stream, so that a back pressure which is influenced by the grain size and the dimensioning of the bed is observed at the entry side. This requires increased power for conveying the gas. On account of the reduced mechanical strength of the substance used in porous form, abrasion occurs, which impedes the gas flow, and this effect may considerably limit the service life of a bed, with the result that the bed has to be exchanged at relatively short intervals of time.
It is known that any substance which is suitable for separation, substantially influenced by the usable surface area and mass, has a limited separation capacity and a saturation range, and consequently complete utilization is not generally possible.
Moreover, during the separation, it is desirable to ensure an approximately constant separation performance over a prolonged period of time. This means separating out a virtually constant quantity (mass) of the component per unit time. Here, however, known solutions have significant deficiencies, since the separation capacity drops over the course of utilization, and this effect occurs well before the saturation limit is reached. A user must accept either a reduced degree of purity of the treated gas or a shorter effective service life. The latter generally means that the separation-regeneration cycle has to be carried out at shorter intervals, which of course entails increased installation and operating costs.